Questions and Answers
What is a characteristic property of most bases and alkalis?
Which of the following is classified as a strong base?
What do strong alkalis form when they react with acidic solutions?
Which of the following bases is commonly used in soap manufacturing?
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What indicates a strong base when measuring pH?
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What type of base will absorb carbon dioxide from the air?
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Which base is specifically used as a drying agent?
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Which statement about diacidic bases is true?
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When bases change the color of indicators, which of the following is the expected action?
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What type of base is formed when a metallic oxide reacts with an acid?
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Study Notes
Universal Indicator and Salts
- Universal indicator consists of a mixture of dyes that display a spectrum of colors based on acidity or alkalinity of a solution.
- Different colors are produced at varying concentrations of hydrogen ions.
- Salts are compounds formed by the replacement of hydrogen atoms of an acid with metallic or ammonium ions.
Classification of Salts
- Normal Salts: Formed by complete replacement of hydrogen ions; e.g., hydrochloric acid yields sodium chloride.
- Acid Salts: Result from partial replacement of hydrogen ions from polybasic acids; e.g., dibasic sulphuric acid yields sodium hydrogen sulphate (NaHSO4).
- Basic Salts: Derived from partial replacement of hydroxyl groups of bases with acid radicals; e.g., basic lead chloride [Pb(OH)Cl].
Acids
- The term 'acid' originates from the Latin word 'acidus,' meaning 'sour.'
- Acids produce hydronium ions (H3O+) when dissolved in water.
Classification of Acids
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By Source:
- Organic Acids: Obtained from plants (e.g., acetic acid, citric acid); weak acids.
- Inorganic Acids: Obtainable from minerals (e.g., hydrochloric acid); strong acids due to complete ionization.
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By Concentration:
- Concentrated Acid: Higher acid content than water.
- Dilute Acid: Higher water content than acid.
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By Basicity:
- Monobasic Acid: Produces one hydronium ion (e.g., HCl).
- Dibasic Acid: Produces two hydronium ions (e.g., sulphuric acid).
- Tribasic Acid: Produces three hydronium ions (e.g., phosphoric acid).
Properties of Acids
- Sour taste and various physical states (solids like boric acid, liquid like HCl).
- Corrosive to skin (e.g., sulfuric acid is black, hydrochloric acid is amber).
- Change indicator colors (blue litmus to red, methyl orange to pink, phenolphthalein remains unchanged).
- Olfactory Indicators: Substances with scent changes in acidic/basic environments (e.g., onion, vanilla, clove oil).
Chemical Properties of Acids
- React with active metals to form hydrogen and metal salts.
- Neutralization reaction with bases.
- React with carbonates to form salt, water, and carbon dioxide.
- Form salt, water, and sulfur dioxide when reacting with sulfites and bisulfites.
- React with sulfides to yield salt and hydrogen sulfide.
- Limited reactions with some chlorides and nitrates.
Bases
- Bases include metallic oxides, metallic hydroxides, or ammonium hydroxide; they react with hydronium ions to form salt and water.
Classification of Bases
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By Strength:
- Strong Base: Completely ionizes in solution.
- Weak Base: Partially ionizes in solution.
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By Acidity:
- Monoacidic Base: Produces one OH- ion.
- Diacidic Base: Produces two OH- ions.
- Triacidic Base: Produces three OH- ions.
Properties of Bases/Alkalis
- Physical properties include a bitter taste, slippery feel, and ability to change indicator colors (e.g., red litmus to blue).
- Strong electrolytes that can absorb carbon dioxide to form carbonates.
- Neutralize acids producing salt and water.
- Precipitate insoluble hydroxides with heavy metal salts (e.g., copper, iron, zinc).
- Release ammonia gas when warmed with ammonium salts.
General Uses of Some Bases
- Sodium Hydroxide: Used in soap manufacturing.
- Potassium Hydroxide: Used to create bleaching powder.
- Magnesia: Utilized in making refractory bricks.
- Calcium Oxide: Functions as a drying agent or basic flux.
Acidic and Basic Solutions
- pH measures the hydrogen ion concentration, calculated as the negative logarithm (base 10) of the concentration expressed in moles per liter.
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Description
Explore the fascinating world of universal indicators and salts in this quiz. Learn how universal indicators change color based on acidity or alkalinity, and discover the classification of salts. Test your knowledge on these fundamental chemistry concepts!
